4. A box of mass 0.50 kg is pulled by a force of magnitude \( F=2.0 \mathrm{~N} \) across a rough, horizontal surface as shown. If the box moves with constant speed along the straight path, what is the total work done on the box when it covers a horizontal distance of 10 m ?

When a box moves with constant speed, the net force acting on it is zero. This means that the applied force (2.0 N) is exactly balanced by the total frictional force opposing the motion. Since the box is not accelerating, the total work done on the box by the net force is zero. However, the work done by the applied force can be calculated by multiplying the force by the distance. In this case, the work done by the applied force is \( W = F \cdot d = 2.0 \, \text{N} \cdot 10 \, \text{m} = 20 \, \text{J} \). The total work done on the box, considering that it is moving at constant speed and that the frictional force does equal and opposite work, is still \( 0 \, \text{J} \) for the net work!